Hi Mike,
You need to look a bit past the way your out of date Tidy
is preconfigured to work from within the HomeSite HTML
editor. If you would prefer it if Tidy gave the "book" answer,
you have to reconfigure it to output XHTML.
R. Scott Granneman's configuration link appeared here aug 13th:
http://www.granneman.com/class/config/tidy/index.htm
There is also a Tidy graphical user interface for Windows,
which greatly eases configuration work, just point and click:
http://perso.wanadoo.fr/ablavier/TidyGUI/
HomeSite support might be willing to help you to get
the changed configuration accepted by their product.